Aptamer Probes Labeled with Lanthanide-Doped Carbon Nanodots Permit Dual-Modal Fluorescence and Mass Cytometric Imaging

High-dimensional imaging mass cytometry (IMC) enables simultaneous quantification of over 35 biomarkers on one tissue section. However, its limited resolution and ultralow acquisition speed remain major issues for general clinical application. Meanwhile, conventional immunofluorescence microscopy (IFM) allows sub-micrometer resolution and rapid identification of the region of interest (ROI), but only operates with low multiplicity. Herein, a series of lanthanide-doped blue-, green-, and red-fluorescent carbon nanodots (namely, B-Cdots(Ln1 ), G-Cdots(Ln2 ), and R-Cdots(Ln3 )) as fluorescence and mass dual-modal tags are developed. Coupled with aptamers, B-Cdots(159 Tb)-A10-3.2, G-Cdots(165 Ho)-AS1411, and R-Cdots(169 Tm)-SYL3C dual-functional aptamer probes, which are then multiplexed with commercially available Maxpar metal-tagged antibodies for analyzing clinical formalin-fixed, paraffin-embedded (FFPE) prostatic adenocarcinoma (PaC) tissue, are further synthesized. The rapid identification of ROI with IFM using fluorescence signals and subsequent multiplexed detection of in situ ROI with IMC using the same tissue section is demonstrated. Dual-modal probes save up to 90% IMC blind scanning time for a standard 3.5 mm × 3.5 mm overall image. Meanwhile, the IFM provides refined details and topological spatial distributions for the functional proteins at optical resolution, which compensates for the low resolution of the IMC imaging.

Deep Learning in Image Cytometry: A Review

Artificial intelligence, deep convolutional neural networks, and deep learning are all niche terms that are increasingly appearing in scientific presentations as well as in the general media. In this review, we focus on deep learning and how it is applied to microscopy image data of cells and tissue samples. Starting with an analogy to neuroscience, we aim to give the reader an overview of the key concepts of neural networks, and an understanding of how deep learning differs from more classical approaches for extracting information from image data. We aim to increase the understanding of these methods, while highlighting considerations regarding input data requirements, computational resources, challenges, and limitations. We do not provide a full manual for applying these methods to your own data, but rather review previously published articles on deep learning in image cytometry, and guide the readers toward further reading on specific networks and methods, including new methods not yet applied to cytometry data. © 2018 The Authors. Cytometry Part A published by Wiley Periodicals, Inc. on behalf of International Society for Advancement of Cytometry.

A portable image-based cytometer for rapid malaria detection and quantification

Increasing resistance by malaria parasites to currently used antimalarials across the developing world warrants timely detection and classification so that appropriate drug combinations can be administered before clinical complications arise. However, this is often challenged by low levels of infection (referred to as parasitemia) and presence of predominantly young parasitic forms in the patients' peripheral blood. Herein, we developed a simple, inexpensive and portable image-based cytometer that detects and numerically counts Plasmodium falciparum infected red blood cells (iRBCs) from Giemsa-stained smears derived from infected blood. Our cytometer is able to classify all parasitic subpopulations by quantifying the area occupied by the parasites within iRBCs, with high specificity, sensitivity and negligible false positives (~ 0.0025%). Moreover, we demonstrate the application of our image-based cytometer in testing anti-malarial efficacy against a commercial flow cytometer and demonstrate comparable results between the two methods. Collectively, these results highlight the possibility to use our image-based cytometer as a cheap, rapid and accurate alternative for antimalarial testing without compromising on efficiency and minimal processing time. With appropriate filters applied into the algorithm, to rule out leukocytes and reticulocytes, our cytometer may also be used for field diagnosis of malaria.

High-Throughput Spectral and Lifetime-Based FRET Screening in Living Cells to Identify Small-Molecule Effectors of SERCA

A robust high-throughput screening (HTS) strategy has been developed to discover small-molecule effectors targeting the sarco/endoplasmic reticulum calcium ATPase (SERCA), based on a fluorescence microplate reader that records both the nanosecond decay waveform (lifetime mode) and the complete emission spectrum (spectral mode), with high precision and speed. This spectral unmixing plate reader (SUPR) was used to screen libraries of small molecules with a fluorescence resonance energy transfer (FRET) biosensor expressed in living cells. Ligand binding was detected by FRET associated with structural rearrangements of green fluorescent protein (GFP, donor) and red fluorescent protein (RFP, acceptor) fused to the cardiac-specific SERCA2a isoform. The results demonstrate accurate quantitation of FRET along with high precision of hit identification. Fluorescence lifetime analysis resolved SERCA's distinct structural states, providing a method to classify small-molecule chemotypes on the basis of their structural effect on the target. The spectral analysis was also applied to flag interference by fluorescent compounds. FRET hits were further evaluated for functional effects on SERCA's ATPase activity via both a coupled-enzyme assay and a FRET-based calcium sensor. Concentration-response curves indicated excellent correlation between FRET and function. These complementary spectral and lifetime FRET detection methods offer an attractive combination of precision, speed, and resolution for HTS.

Spectral Unmixing Plate Reader: High-Throughput, High-Precision FRET Assays in Living Cells

We have developed a microplate reader that records a complete high-quality fluorescence emission spectrum on a well-by-well basis under true high-throughput screening (HTS) conditions. The read time for an entire 384-well plate is less than 3 min. This instrument is particularly well suited for assays based on fluorescence resonance energy transfer (FRET). Intramolecular protein biosensors with genetically encoded green fluorescent protein (GFP) donor and red fluorescent protein (RFP) acceptor tags at positions sensitive to structural changes were stably expressed and studied in living HEK cells. Accurate quantitation of FRET was achieved by decomposing each observed spectrum into a linear combination of four component (basis) spectra (GFP emission, RFP emission, water Raman, and cell autofluorescence). Excitation and detection are both conducted from the top, allowing for thermoelectric control of the sample temperature from below. This spectral unmixing plate reader (SUPR) delivers an unprecedented combination of speed, precision, and accuracy for studying ensemble-averaged FRET in living cells. It complements our previously reported fluorescence lifetime plate reader, which offers the feature of resolving multiple FRET populations within the ensemble. The combination of these two direct waveform-recording technologies greatly enhances the precision and information content for HTS in drug discovery.

Quantifying autophagy: Measuring LC3 puncta and autolysosome formation in cells using multispectral imaging flow cytometry

The use of multispectral imaging flow cytometry has been gaining popularity due to its quantitative power, high throughput capabilities, multiplexing potential and its ability to acquire images of every cell. Autophagy is a process in which dysfunctional organelles and cellular components that accumulate during growth and differentiation are degraded via the lysosome and recycled. During autophagy, cytoplasmic LC3 is processed and recruited to the autophagosomal membranes; the autophagosome then fuses with the lysosome to form the autolysosome. Therefore, cells undergoing autophagy can be identified by visualizing fluorescently labeled LC3 puncta and/or the co-localization of fluorescently labeled LC3 and lysosomal markers. Multispectral imaging flow cytometry is able to collect imagery of large numbers of cells and assess autophagy in an objective, quantitative, and statistically robust manner. This review will examine the four predominant methods that have been used to measure autophagy via multispectral imaging flow cytometry.

Imaging flow cytometry analysis of intracellular pathogens

Imaging flow cytometry has been applied to address questions in infection biology, in particular, infections induced by intracellular pathogens. This methodology, which utilizes specialized analytic software makes it possible to analyze hundreds of quantified features for hundreds of thousands of individual cellular or subcellular events in a single experiment. Imaging flow cytometry analysis of host cell-pathogen interaction can thus quantitatively addresses a variety of biological questions related to intracellular infection, including cell counting, internalization score, and subcellular patterns of co-localization. Here, we provide an overview of recent achievements in the use of fluorescently labeled prokaryotic or eukaryotic pathogens in human cellular infections in analysis of host-pathogen interactions. Specifically, we give examples of Imagestream-based analysis of cell lines infected with Toxoplasma gondii or Mycobacterium tuberculosis. Furthermore, we illustrate the capabilities of imaging flow cytometry using a combination of standard IDEAS™ software and the more recently developed Feature Finder algorithm, which is capable of identifying statistically significant differences between researcher-defined image galleries. We argue that the combination of imaging flow cytometry with these software platforms provides a powerful new approach to understanding host control of intracellular pathogens.

Quantifying MHC dextramer-induced NFAT activation in antigen-specific T cells as a functional response parameter

MHC-multimers are reagents used for the detection and enumeration of antigen-specific T cells (ASTs). These reagents exploit the mechanism by which T cell receptors (TCR) on cytotoxic CD8 T cells recognize specific antigens in the context of a major histocompatibility complex (MHC) molecule during antigen presentation. MHC-multimers are fluorescently-labeled dextran polymers that carry MHC Class I molecules and peptide sequences that can be modified to represent specific cognate sequences of the antigen of interest with dextramers having a 10-fold multiplicity of the MHC/peptide combination within a single multimer. Since the binding of antigen-specific dextramers mimics antigen presentation to the TCR, the present study sought to determine whether this TCR engagement on the AST was sufficient to elicit a functional T cell response. The effect of binding of CMV specific dextramers on the activation of the NFAT signal transduction cascade was assessed in peripheral blood from bone marrow transplant recipients previously determined to be positive for CMV-ASTs (CASTs). NFAT activation was quantified by measuring nuclear translocation of NFAT1 in CD8+ CASTs and CD8+ non-CASTs by imaging flow cytometry. Our results demonstrate that an increase in the nuclear localization of NFAT1 was detectable in the CASTs following the CMV-dextramer binding and could be observed as early as 10min post-exposure. The NFAT1 activation correlated with a downstream functional response in the form of interferon gamma production. Sample preparation, temperature, and duration of dextramer exposure were important parameters affecting the dextramer-induced NFAT activation with 2h exposure in whole blood at room temperature being the optimal of the conditions tested. Intra- and inter-individual heterogeneity was observed with regards to the NFAT activation in the CASTs. Importantly, no effect of the dextramers was observed in the CD8+ non-CASTs, and therefore dextramer negative cell populations. Exposure to PMA/ionomycin following dextramer exposure resulted in a homogeneous NFAT activation in both the dextramer-positive but NFAT1 nonresponsive CAST and non-CAST cells. Thus, the data demonstrate that binding of antigen-specific dextramers to ASTs specifically results in activation of NFAT, that the NFAT activation correlates with a downstream functional response and that the response can be heterogeneous. This functional parameter may provide insight to the issue whether enumeration alone of ASTs is a sufficient parameter to assess an individual's immune status against a specific antigen.

Implementation and application of a novel 2D magnetic twisting cytometry based on multi-pole electromagnet

We implemented a novel 2D magnetic twisting cytometry (MTC) based on a previously reported multi-pole high permeability electromagnet, in which both the strength and direction of the twisting field can be controlled. Thanks to the high performance twisting electromagnet and the heterodyning technology, the measurement frequency has been extended to the 1 kHz range. In order to obtain high remanence of the ferromagnetic beads, a separate electromagnet with feedback control was adopted for the high magnetic field polarization. Our setup constitutes the first instrument which can be operated both in MTC mode and in magnetic tweezers (MT) mode. In this work, the mechanical properties of HL-1 cardiomyocytes were characterized in MTC mode. Both anisotropy and log-normal distribution of cell stiffness were observed, which agree with our previous results measured in MT mode. The response from these living cells at different frequencies can be fitted very well by the soft glassy rheology model.

FlowCam: Quantification and Classification of Phytoplankton by Imaging Flow Cytometry

The ability to enumerate, classify, and determine biomass of phytoplankton from environmental samples is essential for determining ecosystem function and their role in the aquatic community and microbial food web. Traditional micro-phytoplankton quantification methods using microscopic techniques require preservation and are slow, tedious and very laborious. The availability of more automated imaging microscopy platforms has revolutionized the way particles and cells are detected within their natural environment. The ability to examine cells unaltered and without preservation is key to providing more accurate cell concentration estimates and overall phytoplankton biomass. The FlowCam(®) is an imaging cytometry tool that was originally developed for use in aquatic sciences and provides a more rapid and unbiased method for enumerating and classifying phytoplankton within diverse aquatic environments.

Quantitative Functional Morphology by Imaging Flow Cytometry

This chapter describes advantages and limitations of imaging flow cytometry (IFC) based on Imagestream instrumentation using a hybrid approach of morphometric measurement and quantitation of multiparametric fluorescent intensities' distribution in cells and particles. Brief comparison is given of IFC with conventional flow cytometry and fluorescent microscopy. Some future directions of the IFC technology are described and discussed.

A widefield fluorescence microscope with a linear image sensor for image cytometry of biospecimens: Considerations for image quality optimization

Linear image sensors have been widely used in numerous research and industry applications to provide continuous imaging of moving objects. Here, we present a widefield fluorescence microscope with a linear image sensor used to image translating objects for image cytometry. First, a calibration curve was characterized for a custom microfluidic chamber over a span of volumetric pump rates. Image data were also acquired using 15 μm fluorescent polystyrene spheres on a slide with a motorized translation stage in order to match linear translation speed with line exposure periods to preserve the image aspect ratio. Aspect ratios were then calculated after imaging to ensure quality control of image data. Fluorescent beads were imaged in suspension flowing through the microfluidics chamber being pumped by a mechanical syringe pump at 16 μl min(-1) with a line exposure period of 150 μs. The line period was selected to acquire images of fluorescent beads with a 40 dB signal-to-background ratio. A motorized translation stage was then used to transport conventional glass slides of stained cellular biospecimens. Whole blood collected from healthy volunteers was stained with 0.02% (w/v) proflavine hemisulfate was imaged to highlight leukocyte morphology with a 1.56 mm × 1.28 mm field of view (1540 ms total acquisition time). Oral squamous cells were also collected from healthy volunteers and stained with 0.01% (w/v) proflavine hemisulfate to demonstrate quantifiable subcellular features and an average nuclear to cytoplasmic ratio of 0.03 (n = 75), with a resolution of 0.31 μm pixels(-1).

[THE VIRTUAL CYTOLOGIC SLIDES FOR EXTERNAL EVALUATION OF QUALITY OF IMPLEMENTATION OF CYTOLOGIC ANALYSES IN CLINICAL DIAGNOSTIC LABORATORIES: POSSIBILITIES AND PERSPECTIVES]

The article considers application of technology of analysis of cytological slides in external quality control of clinical diagnostic laboratories. The advantages of virtual slides are demonstrated against other applied technologies of external evaluation of quality i.e. slide plate and digital micro-photography. The conditions of formation of virtual slides for external evaluation of quality of clinical diagnostic laboratories. The technology of their application is described. The success of practical application of considered technology in the Federal system of external evaluation of quality is emphasized.

Levitational Image Cytometry with Temporal Resolution

A simple, yet powerful magnetic-levitation-based device is reported for real-time, label-free separation, as well as high-resolution monitoring of cell populations based on their unique magnetic and density signatures. This method allows a wide variety of cellular processes to be studied, accompanied by transient or permanent changes in cells' fundamental characteristics as a biological material.

Ultrafast automated image cytometry for cancer detection

We present a method for ultrafast automated single-cell optical microscopy that performs blur-free image acquisition and non-stop real-time image-recording and classification of cells during high-speed flow. This method is based on a unique integration of ultrafast optical imaging, self-focusing microfluidics, optoelectronics, and information technology. To show the system's utility, we demonstrate high-throughput image-based screening of rare breast cancer cells in blood with an unprecedented throughput of 100,000 cells/s and a record false positive rate of one in a million. This method is expected to be effective for early, noninvasive, low-cost detection of cancer.

Lensfree computational microscopy tools for cell and tissue imaging at the point-of-care and in low-resource settings

The recent revolution in digital technologies and information processing methods present important opportunities to transform the way optical imaging is performed, particularly toward improving the throughput of microscopes while at the same time reducing their relative cost and complexity. Lensfree computational microscopy is rapidly emerging toward this end, and by discarding lenses and other bulky optical components of conventional imaging systems, and relying on digital computation instead, it can achieve both reflection and transmission mode microscopy over a large field-of-view within compact, cost-effective and mechanically robust architectures. Such high throughput and miniaturized imaging devices can provide a complementary toolset for telemedicine applications and point-of-care diagnostics by facilitating complex and critical tasks such as cytometry and microscopic analysis of e.g., blood smears, Papanicolaou (Pap) tests and tissue samples. In this article, the basics of these lensfree microscopy modalities will be reviewed, and their clinically relevant applications will be discussed.

Phase imaging flow cytometry using a focus-stack collecting microscope

This letter introduces a fluidics-based focus-stack collecting microscope. A microfluidic device transports cells through the focal plane of a microscope, resulting in an efficient method to collect focus stacks of large collections of single cells. Images from the focus stacks are used to reconstruct the quantitative phase of cells with the transport-of-intensity-equation method. Using the phase imaging flow cytometer, we measure three-dimensional shape variations of red blood and leukemia cells.

A novel method for kinetic measurements of rare cell proliferation using Cellometer image-based cytometry

Cell proliferation is an important assay for pharmaceutical and biomedical research to test the effects of a variety of treatments on cultured primary cells or cell lines. For immunological studies, the ability to perform rapid cell proliferation analysis allows the identification of potential biological reagents for inducing or inhibiting immune cell proliferation. Current cell proliferation analysis methods employ flow cytometry for fluorescence detection of CFSE-labeled cells. However, conventional flow cytometers require a considerable amount of cells per sample, which becomes an issue for kinetic measurements with rare cell population due to the lack of samples for flow cytometric analyses at multiple time points during proliferation period. Here we report the development of a novel cell proliferation kinetic detection method for low cell concentration samples using the new Cellometer Vision system. Since the Cellometer system requires only 20 μl of sample, cell proliferation can be measured at multiple time points over the entire culturing period, whereas typically, flow cytometry is only performed at the end of the proliferation period. To validate the detection method, B1 and B2 B cells were treated with a B cell mitogen for 6 days, and proliferation was measured using Cellometer on day 1, 3, 5, and 6. To demonstrate the capability of the system, B1 B cells were treated with a panel of TLR agonists (Pam3Cys, PolyIC, CLO97, and CpG) for 7 days, and proliferation was measured on day 2, 4, 6, and 7. Cellometer image-based cytometry (IBC) was able to obtain proliferation results on each day with the last time point comparable to flow cytometry. This novel method allows for kinetic measurements of the rare cell samples such as B1 B cell, which has the potential to revolutionize kinetic analysis of cell proliferation.

In vivo plant flow cytometry: a first proof-of-concept

In vivo flow cytometry has facilitated advances in the ultrasensitive detection of tumor cells, bacteria, nanoparticles, dyes, and other normal and abnormal objects directly in blood and lymph circulatory systems. Here, we propose in vivo plant flow cytometry for the real-time noninvasive study of nanomaterial transport in xylem and phloem plant vascular systems. As a proof of this concept, we demonstrate in vivo real-time photoacoustic monitoring of quantum dot-carbon nanotube conjugates uptake by roots and spreading through stem to leaves in a tomato plant. In addition, in vivo scanning cytometry using multimodal photoacoustic, photothermal, and fluorescent detection schematics provided multiplex detection and identification of nanoparticles accumulated in plant leaves in the presence of intensive absorption, scattering, and autofluorescent backgrounds. The use of a portable fiber-based photoacoustic flow cytometer for studies of plant vasculature was demonstrated. These integrated cytometry modalities using both endogenous and exogenous contrast agents have a potential to open new avenues of in vivo study of the nutrients, products of photosynthesis and metabolism, nanoparticles, infectious agents, and other objects transported through plant vasculature.

Lensless imaging for simultaneous microfluidic sperm monitoring and sorting

5.3 million American couples of reproductive age (9%) are affected by infertility, among which male factors account for up to 50% of cases, which necessitates the identification of parameters defining sperm quality, including sperm count and motility. In vitro fertilization (IVF) with or without intra cytoplasmic sperm injection (ICSI) has become the most widely used assisted reproductive technology (ART) in modern clinical practice to overcome male infertility challenges. One of the obstacles of IVF and ICSI lies in identifying and isolating the most motile and presumably healthiest sperm from semen samples that have low sperm counts (oligozoospermia) and/or low sperm motility (oligospermaesthenia). Microfluidic systems have shown potential to sort sperm with flow systems. However, the small field of view (FOV) of conventional microscopes commonly used to image sperm motion presents challenges in tracking a large number of sperm cells simultaneously. To address this challenge, we have integrated a lensless charge-coupled device (CCD) with a microfluidic chip to enable wide FOV and automatic recording as the sperm move inside a microfluidic channel. The integrated system enables the sorting and tracking of a population of sperm that have been placed in a microfluidic channel. This channel can be monitored in both horizontal and vertical configuration similar to a swim-up column method used clinically. Sperm motilities can be quantified by tracing the shadow paths for individual sperm. Moreover, as the sperm are sorted by swimming from the inlet towards the outlet of a microfluidic channel, motile sperm that reach the outlet can be extracted from the channel at the end of the process. This technology can lead to methods to evaluate each sperm individually in terms of motility response in a wide field of view, which could prove especially useful, when working with oligozoospermic or oligospermaesthenic samples, in which the most motile sperm need to be isolated from a pool of small number of sperm.

High-content screening of drug-induced cardiotoxicity using quantitative single cell imaging cytometry on microfluidic device

Drug-induced cardiotoxicity or cytotoxicity followed by cell death in cardiac muscle is one of the major concerns in drug development. Herein, we report a high-content quantitative multicolor single cell imaging tool for automatic screening of drug-induced cardiotoxicity in an intact cell. A tunable multicolor imaging system coupled with a miniaturized sample platform was destined to elucidate drug-induced cardiotoxicity via simultaneous quantitative monitoring of intracellular sodium ion concentration, potassium ion channel permeability and apoptosis/necrosis in H9c2(2-1) cell line. Cells were treated with cisapride (a human ether-à-go-go-related gene (hERG) channel blocker), digoxin (Na(+)/K(+)-pump blocker), camptothecin (anticancer agent) and a newly synthesized anti-cancer drug candidate (SH-03). Decrease in potassium channel permeability in cisapride-treated cells indicated that it can also inhibit the trafficking of the hERG channel. Digoxin treatment resulted in an increase of intracellular [Na(+)]. However, it did not affect potassium channel permeability. Camptothecin and SH-03 did not show any cytotoxic effect at normal use (≤300 nM and 10 μM, respectively). This result clearly indicates the potential of SH-03 as a new anticancer drug candidate. The developed method was also used to correlate the cell death pathway with alterations in intracellular [Na(+)]. The developed protocol can directly depict and quantitate targeted cellular responses, subsequently enabling an automated, easy to operate tool that is applicable to drug-induced cytotoxicity monitoring with special reference to next generation drug discovery screening. This multicolor imaging based system has great potential as a complementary system to the conventional patch clamp technique and flow cytometric measurement for the screening of drug cardiotoxicity.

The cytometric future: it ain't necessarily flow!

Initial approaches to cytometry for classifying and characterizing cells were based on microscopy; it was necessary to collect relatively high-resolution images of cells because only a few specific reagents usable for cell identification were available. Although flow cytometry, now the dominant cytometric technology, typically utilizes lenses similar to microscope lenses for light collection, improved, more quantitative reagents allow the necessary information to be acquired in the form of whole-cell measurements of the intensities of light transmission, scattering, and/or fluorescence.Much of the cost and complexity of both automated microscopes and flow cytometers arises from the necessity for them to measure one cell at a time. Recent developments in digital camera technology now offer an alternative in which one or more low-magnification, low-resolution images are made of a wide field containing many cells, using inexpensive light-emitting diodes (LEDs) for illumination. Minimalist widefield imaging cytometers can provide a smaller, less complex, and substantially less expensive alternative to flow cytometry, critical in systems intended for in resource-poor areas. Minimalism is, likewise, a good philosophy in developing instrumentation and methodology for both clinical and large-scale research use; it simplifies quality assurance and compliance with regulatory requirements, as well as reduces capital outlays, material costs, and personnel training requirements. Also, importantly, it yields "greener" technology.

Cytometry in cell necrobiology revisited. Recent advances and new vistas

Over a decade has passed since publication of the last review on "Cytometry in cell necrobiology." During these years we have witnessed many substantial developments in the field of cell necrobiology such as remarkable advancements in cytometric technologies and improvements in analytical biochemistry. The latest innovative platforms such as laser scanning cytometry, multispectral imaging cytometry, spectroscopic cytometry, and microfluidic Lab-on-a-Chip solutions rapidly emerge as highly advantageous tools in cell necrobiology studies. Furthermore, we have recently gained substantial knowledge on alternative cell demise modes such as caspase-independent apoptosis-like programmed cell death (PCD), autophagy, necrosis-like PCD, or mitotic catastrophe, all with profound connotations to pathogenesis and treatment. Although detection of classical, caspase-dependent apoptosis is still the major ground for the advancement of cytometric techniques, there is an increasing demand for novel analytical tools to rapidly quantify noncanonical modes of cell death. This review highlights the key developments warranting a renaissance and evolution of cytometric techniques in the field of cell necrobiology.

Morphology-based assessment of Cd2+ cytotoxicity using microfluidic image cytometry (microFIC)

Microfluidic systems have significant implications in the field of in vitro cell-based assays since they may allow conventional cell-based assays to be conducted in an automated and high-throughput fashion. In this study, we combined a simple microfluidic cells-on-chip system with a morphology-based image cytometric analysis approach for the assessment of Cd(2+) induced apoptosis of Chang liver cell line. A simple and efficient in situ monitoring method for quantifying the progress of a cell death event was developed and is presented here. Reasonable agreement of the estimated EC(50) value from this study with those from the literature and a close correlation between the observed changes in cell morphology (i.e., circularity) and the amount of reactive oxygen species (ROS) generation confirmed the validity of this morphology-based microfluidic image cytometric (microFIC) assessment method. We propose this morphology-based microFIC approach as an easy and efficient way to assess cytotoxicity which can be adapted to high-throughput screening platforms for in vitro cytotoxicity assays as well as drug screening.

Identification of antigen-specific B cells by concurrent monitoring of intracellular Ca2+ mobilization and antigen binding with microwell array chip system equipped with a CCD imager

B cells are very heterogeneous, consisting of more than 10(9) B-cell clones with distinct specificities for antigens in each individual. To identify single B cells with antigen specificity, we have been developing cell microarray technology using microwell array chips whose microwells each capture a single B cell. Using microwell array chips, we detected antigen-specific B cells by monitoring antigen-induced intracellular Ca2+ mobilization with a CCD scanner (MAC-CCD system) or the binding of fluorescence-labeled antigen to cells with a confocal laser scanner. We retrieved target cells from the chip, cloned immunoglobulin genes, and produced antigen-specific antibodies. However, these methods present some difficulties: the former technique could not detect cells whose frequency was less than 0.05% and the latter one took a long time to identify the objective cells although it could detect cells at a frequency of 0.01%. Here, we have combined the advantages of these two methods. Monitoring antigen-induced intracellular Ca2+ mobilizations and the binding of fluorescence-labeled antigens simultaneously with a MAC-CCD system enabled us to detect rapidly, antigen-specific B cells whose frequency was less than 0.01% with high efficiency. Our system provides a superior screening system for antigen-specific B cells and extends the horizons of multiparameter single-cell analysis in heterogeneous cell populations.

Light microscopy digital imaging

This unit presents an overview of digital imaging hardware used in light microscopy. CMOS, CCD, and EMCCDs are the primary sensors used. The strengths and weaknesses of each define the primary applications for these sensors. Sensor architecture and formats are also reviewed. Color camera design strategies and sensor window cleaning are also described in the unit.

Two-photon imaging of spatially extended neuronal network dynamics with high temporal resolution

We describe a simple two-photon fluorescence imaging strategy, called targeted path scanning (TPS), to monitor the dynamics of spatially extended neuronal networks with high spatiotemporal resolution. Our strategy combines the advantages of mirror-based scanning, minimized dead time, ease of implementation, and compatibility with high-resolution low-magnification objectives. To demonstrate the performance of TPS, we monitor the calcium dynamics distributed across an entire juvenile rat hippocampus (>1.5mm), at scan rates of 100 Hz, with single cell resolution and single action potential sensitivity. Our strategy for fast, efficient two-photon microscopy over spatially extended regions provides a particularly attractive solution for monitoring neuronal population activity in thick tissue, without sacrificing the signal-to-noise ratio or high spatial resolution associated with standard two-photon microscopy. Finally, we provide the code to make our technique generally available.

CD4+ T lymphocytes enumeration by an easy-to-use single platform image cytometer for HIV monitoring in resource-constrained settings

BACKGROUND

HIV monitoring in resource-constrained settings demands affordable and reliable CD4(+) T lymphocytes enumeration methods. We developed a simple single platform image cytometer (SP ICM), which is a dedicated volumetric CD4(+) T lymphocytes enumeration system that uses immunomagnetic and immunofluorescent technologies. The instrument was designed to be a low-cost, yet reliable and robust one. In this article we test the instrument and the immunochemical procedures used on blood from HIV negative and HIV positive patients.

METHODS

After CD4 immunomagnetic labeling in whole blood, CD4(+) T lymphocytes, CD4(+dim) monocytes and some nonspecifically labeled cells are magnetically attracted to an analysis surface. Combining with CD3-Phycoerythrin (PE) labeling, only CD3(+)CD4(+) T lymphocytes are fluorescently labeled and visible in a fluorescent image of the analysis surface. The number of CD4(+) T lymphocytes is obtained by image analysis. Alternatively, CD3 immunomagnetic selection in combination with CD4 immunofluorescent labeling can also be applied for CD4(+) T lymphocytes enumeration.

RESULTS

The SP ICM system was compared with two single platform flow cytometer (SP FCM) methods: tetraCXP and TruCount methods. The SP ICM system has excellent precision, accuracy and linearity for CD4(+) T lymphocytes enumeration. Good correlations were obtained between the SP ICM and the SP FCM methods for blood specimens of 44 HIV(-) patients, and of 63 HIV(+) patients. Bland-Altman plots showed interchangeability between the SP ICM and the SP FCM methods.

CONCLUSIONS

The immunolabeling methods and the instrumentation are simple and easy-to-handle for less-trained operators. The SP ICM system is a good candidate for CD4(+) T lymphocytes enumeration in point-of-care settings of resource-constrained countries.

Binary imaging analysis for comprehensive quantitative histomorphometry of peripheral nerve

Quantitative histomorphometry is the current gold standard for objective measurement of nerve architecture and its components. Many methods still in use rely heavily upon manual techniques that are prohibitively time consuming, predisposing to operator fatigue, sampling error, and overall limited reproducibility. More recently, investigators have attempted to combine the speed of automated morphometry with the accuracy of manual and semi-automated methods. Systematic refinements in binary imaging analysis techniques combined with an algorithmic approach allow for more exhaustive characterization of nerve parameters in the surgically relevant injury paradigms of regeneration following crush, transection, and nerve gap injuries. The binary imaging method introduced here uses multiple bitplanes to achieve reproducible, high throughput quantitative assessment of peripheral nerve. Number of myelinated axons, myelinated fiber diameter, myelin thickness, fiber distributions, myelinated fiber density, and neural debris can be quantitatively evaluated with stratification of raw data by nerve component. Results of this semi-automated method are validated by comparing values against those obtained with manual techniques. The use of this approach results in more rapid, accurate, and complete assessment of myelinated axons than manual techniques.

Segmentation of cultured neurons using logical analysis of grey and distance difference

The molecular and cellular bases of neuronal cell death that underpin a wide range of neurodegenerative disorders are still not well understood. One approach to investigating neuronal death is through systematic studies of the changing morphology of cultured brain neurons in response to cellular challenges. Image segmentation methods developed to date to analyze such changes have been limited by the low contrast of cells in unstained neuronal cultures and the unimodal histograms generated by these analyses. In this paper we present new algorithms based on logical analysis of grey and distance difference of images that successfully circumvent these problems. Two key parameters of this analysis, window width and logical threshold, are automatically extracted for use in logical level technique, and spurious regions are detected and removed through use of a hierarchical window filter. The efficacy of the developed algorithms is demonstrated here through an analysis of cultured brain neurons from newborn mice.

Stereological and somatotopic analysis of the spinal microglial response to peripheral nerve injury

The involvement of glia, and glia-neuronal signalling in enhancing nociceptive transmission has become an area of intense scientific interest. In particular, a role has emerged for activated microglia in the development and maintenance of neuropathic pain following peripheral nerve injury. Following activation, spinal microglia proliferate and release many substances which are capable of modulating neuronal excitability within the spinal cord. Here, we the investigated the response of spinal microglia to a unilateral spared nerve injury (SNI) in terms of the quantitative increase in cell number and the spatial distribution of the increase. Design-based stereological techniques were combined with iba-1 immunohistochemistry to estimate the total number of microglia in the spinal dorsal horn in naïve and peripheral nerve-injured adult rats. In addition, by mapping the central terminals of hindlimb nerves, the somatotopic distribution of the microglial response was mapped. Following SNI there was a marked increase in the number of spinal microglia: The total number of microglia (mean+/-SD) in the dorsal horn sciatic territory of the naïve rat was estimated to be 28,591+/-2715. Following SNI the number of microglia was 82,034+/-8828. While the pattern of microglial activation generally followed somatotopic boundaries, with the majority of microglia within the territory occupied by peripherally axotomised primary afferents, some spread was seen into regions occupied by intact, 'spared' central projections of the sural nerve. This study provides a reproducible method of assaying spinal microglial dynamics following peripheral nerve injury both quantitatively and spatially.

A single platform image cytometer for resource-poor settings to monitor disease progression in HIV infection

BACKGROUND

For resource-poor countries, affordable methods are required for enumeration of CD4(+) T lymphocytes of HIV-positive patients. For infants, additional determination of CD4/CD8 ratio is needed.

METHODS

We determine the CD4(+) and CD8(+) T lymphocytes as the CD3(+)CD4(+) and CD3(+)CD8(+) population of blood cells. Target cells are CD3-immunomagnetically separated from the whole blood, and CD4-Phycoerythrin and CD8-PerCP immunofluorescently labeled. A point-of-care single platform image cytometer was developed to enumerate the target CD3(+)CD4(+) and CD3(+)CD8(+) populations. It has light-emitting diodes illumination, is fully computer-controlled, operates from a 12 V battery, and was designed to be cheap and easy-to-handle. Target cells are imaged on a CCD camera and enumerated by an image analysis algorithm. The cytometer outputs the absolute number of CD4(+) and CD8(+) T lymphocytes/microl and CD4/CD8 ratio.

RESULTS

The quality of the cell images obtained with the cytometer is sufficient for a reliable enumeration of target cells. The image cytometer achieves an accuracy of better than 10% in the range of 50-1700 cells/microl. Analysis of blood samples from HIV patients yields a good agreement with the TruCount method for CD4 and CD8 count and CD4/CD8 ratio.

CONCLUSIONS

The image cytometer is affordable (component costs $3,000), compact (25 x 25 x 20 cm(3)), and uses disposable test materials, making it a good candidate to monitor progression of immunodeficiency disease in resource-poor settings.

An immunomagnetic single-platform image cytometer for cell enumeration based on antibody specificity

Simplification of cell enumeration technologies is necessary, especially for resource-poor countries, where reliable and affordable enumeration systems are greatly needed. In this paper, an immunomagnetic single-platform image cytometer (SP ICM) for cell enumeration based on antibody specificity is reported. A chamber/magnet assembly was designed such that the immunomagnetically labeled, acridine orange-stained cells in a blood sample moved to the surface of the chamber, where a fluorescent image was captured and analyzed for cell enumeration. The system was evaluated by applying one kind of antibody to count leukocytes and one kind for each leukocyte subpopulation: CD45 for leukocytes, CD3 for T lymphocytes, and CD19 for B lymphocytes. Excellent precision and linearity were achieved. Moreover, these cell counts, each from blood specimens of 42 to 52 randomly selected patients, were compared with those obtained by SP (TruCount) and dual-platform (DP) flow cytometry (FCM) technologies. The cell counts obtained by our system were in between those obtained from the TruCount and DP FCM methods; and good correlations were achieved (R > or = 0.95). For CD4(+) counts, as we expected, the cell count by our system was significantly higher than the CD4(+) T-lymphocyte counts obtained by SP and DP FCM methods. Immunophenotyping of the immunomagnetically selected CD4(+) cells showed that, besides CD4(+) T lymphocytes, a proportion of the CD4(+) dim monocytes was also selected. Our system is a simple immunomagnetic SP ICM, which can potentially be used for enumeration of CD3(+) CD4(+) T lymphocytes in resource-poor countries if an additional CD3 immunofluorescent label is applied.

The ImageStream System: a key step to a new era in imaging

The aim of this article is to provide a brief review about the ImageStream system a novel tool for multiparameter cell analysis in flow. The instrument integrates the features of flow cytometry and fluorescence microscopy combined with a modern methodology for image analysis. Similar to flow cytometry, ImageStream allows analysis of a large number of cells based on their fluorescence features and provides statistical analysis of these features. Additionally, ImageStream allows detailed morphometric cellular analysis based on acquired cellular images integrating various morphometric and photometric features of the examined cells. Simply stated, ImageStream system is an advanced flow cytometer acquiring both integrated fluorescence signals as well as high quality fluorescence images and allowing muliparameter analysis. The innovative features of the instrument offer new analytical capabilities and allow for a multitude of possible applications beyond the current means of flow cytometry. While this article summarizes basic information about the features of ImageStream and its applications based on the available literature and it also describes our own experience.

High-resolution whole organ imaging using two-photon tissue cytometry

Three-dimensional (3-D) tissue imaging offers substantial benefits to a wide range of biomedical investigations from cardiovascular biology, diabetes, Alzheimer's disease to cancer. Two-photon tissue cytometry is a novel technique based on high-speed multiphoton microscopy coupled with automated histological sectioning, which can quantify tissue morphology and physiology throughout entire organs with subcellular resolution. Furthermore, two-photon tissue cytometry offers all the benefits of fluorescence-based approaches including high specificity and sensitivity and appropriateness for molecular imaging of gene and protein expression. We use two-photon tissue cytometry to image an entire mouse heart at subcellular resolution to quantify the 3-D morphology of cardiac microvasculature and myocyte morphology spanning almost five orders of magnitude in length scales.

Imaging spectrometer fundamentals for researchers in the biosciences--a tutorial

Over the last 2 years there has been a dramatic increase in the number of bioscience laboratories using wavelength dispersive spectroscopy to study in vivo, in situ fluorescence. Transforming spectral information into an image provides a graphic means of mapping localized ionic, molecular, and protein-protein interactions. Spectroscopy also enables fluorophores with overlapping spectral features to be delineation. In this study, we provide the tools that a researcher needs to put into perspective instrumental contributions to a reported spectrum in order to gain greater understanding of the natural emission of the sample. We also show how to deduce the basic capabilities of a spectral confocal system. Finally, we show how to determine the true spectral bandwidth of an object, the illuminated area of a laser-excited object, and what is needed to optimize light throughput.

From imaging to understanding: Frontiers in Live Cell Imaging, Bethesda, MD, April 19-21, 2006

A recent meeting entitled Frontiers in Live Cell Imaging was attended by more than 400 cell biologists, physicists, chemists, mathematicians, and engineers. Unlike typical special topics meetings, which bring together investigators in a defined field primarily to review recent progress, the purpose of this meeting was to promote cross-disciplinary interactions by introducing emerging methods on the one hand and important biological applications on the other. The goal was to turn live cell imaging from a "technique" used in cell biology into a new exploratory science that combines a number of research fields.

Personal cytometers: slow flow or no flow?

BACKGROUND

Although some manufacturers have optimistically described instruments with prices in the 40,000 US dollars range as "personal cytometers", analogy with the personal computer suggests that the target price for a true "personal" cytometer should be under 5,000 US dollars. Since such an apparatus could find a wide range of applications in cytomics in both developing and developed countries, it seemed desirable to consider its technical and economic feasibility.

METHODS

Using resolution targets and a variety of fluorescent bead standards immobilized on filters and/or slides, we evaluated high-intensity LEDs as fluorescence excitation sources, relatively inexpensive CCD cameras as detectors, and 35 mm camera lenses and plastic low-power microscope optics for light collection in a simple, inexpensive low-resolution imaging cytometer.

RESULTS

The components tested could be combined toproduce an instrument capable of detecting fewer than 10,000 molecules of cell-associated fluorescent label, and thus applicable to a broad range of cytometric tasks.

CONCLUSIONS

Given the requirements for light sources, detectors, optics, mechanics, electronics and data analysis hardware and software, and the components presently available, it should be easier to reach the desired 5,000 US dollars price point with an image cytometer than with a flow cytometer.

Toward complete laser ablation of melanoma contaminant cells in a co-culture outgrowth model via image cytometry

BACKGROUND

Contaminant cancer cells in autologous transplant tissue can cause relapse and the rates are unknown. A method capable of removing all contaminant cells with a high probability detected by cytomic analyses would be useful. Neither 100% cell purging nor techniques for measuring the probability of success have been developed. Here, we report a method for removing 100% of the cells under ideal staining conditions and quantify the probability of success.

METHODS

Laser ablation was combined with previously reported automated microscopy to purge contaminant cells and evaluate 100% ablation in a co-culture model of prestained mouse melanoma cells mixed with mouse NIH-3T3 cells. Melanoma passage efficiency was measured by: (1) micropipetting single cells into microtiter wells and (2) ablating all but one melanoma cell in co-cultures.

RESULTS

(74 +/- 5)% of single melanoma cells pipetted into microtiter plate wells divided at least once. With ablation of all but one contaminant cell in co-cultures, melanoma dominated in (62 +/- 8)% cultures in 21 days. With 100% ablation in six additional experiments, no melanoma outgrowth was observed, giving a >99.1% probability that all contaminant melanoma cells were purged.

CONCLUSIONS

We successfully demonstrated a model for complete ablation within a defined probability using automated high-content image cytometry with ideal staining conditions. The results show that the instrumentation is capable of delivering 100% ablation at a defined probability and establishes the basis for further studies with clinical models wherein pretherapeutic cytomic analyses of unique cellular expression and/or morphological characteristics will be key for contaminant cancer cell identification.

Slide-based cytometry for cytomics--a minireview

In the postgenomic era, to gain the most detailed quantitative data from biological specimens has become increasingly important in the emerging new fields of high-content and high-throughput single-cell analysis for systems biology and cytomics. Areas of research and diagnosis with the demand to virtually measure "anything" in the cell include immunophenotyping, rare cell detection and characterization in the case of stem cells and residual tumor cells, tissue analysis, and drug discovery. Systemic analysis is also a prerequisite for predictive medicine by genomics, proteomics, and cytomics. This issue of Cytometry Part A is dedicated to innovative concepts of system wide single cells analysis and manipulation, new technologies, data analysis and display, and, finally, quality assessment. The manuscripts to these chapters are provided by cutting edge experts in the fields. This overview will briefly highlight the most important aspects of this continuously developing field.

Spectral imaging perspective on cytomics

BACKGROUND

Cytomics involves the analysis of cellular morphology and molecular phenotypes, with reference to tissue architecture and to additional metadata. To this end, a variety of imaging and nonimaging technologies need to be integrated. Spectral imaging is proposed as a tool that can simplify and enrich the extraction of morphological and molecular information. Simple-to-use instrumentation is available that mounts on standard microscopes and can generate spectral image datasets with excellent spatial and spectral resolution; these can be exploited by sophisticated analysis tools.

METHODS

This report focuses on brightfield microscopy-based approaches. Cytological and histological samples were stained using nonspecific standard stains (Giemsa; hematoxylin and eosin (H&E)) or immunohistochemical (IHC) techniques employing three chromogens plus a hematoxylin counterstain. The samples were imaged using the Nuance system, a commercially available, liquid-crystal tunable-filter-based multispectral imaging platform. The resulting data sets were analyzed using spectral unmixing algorithms and/or learn-by-example classification tools.

RESULTS

Spectral unmixing of Giemsa-stained guinea-pig blood films readily classified the major blood elements. Machine-learning classifiers were also successful at the same task, as well in distinguishing normal from malignant regions in a colon-cancer example, and in delineating regions of inflammation in an H&E-stained kidney sample. In an example of a multiplexed ICH sample, brown, red, and blue chromogens were isolated into separate images without crosstalk or interference from the (also blue) hematoxylin counterstain.

CONCLUSION

Cytomics requires both accurate architectural segmentation as well as multiplexed molecular imaging to associate molecular phenotypes with relevant cellular and tissue compartments. Multispectral imaging can assist in both these tasks, and conveys new utility to brightfield-based microscopy approaches.

In vivo cytometry: a spectrum of possibilities

BACKGROUND

We investigate whether optical imaging can reliably detect abnormalities in tissue, in a range of specimens (live cells in vitro; fixed, fresh ex-vivo and in vivo tissue), without the use of added contrast agents, and review our promising spectral methods for achieving quantitative, real-time, high resolution intrasurgical optical diagnostics.

METHODS

We use reflectance, fluorescence, two-photon, and Mie scattering imaging, performed with instrumentation we developed or modified, to detect intrinsic tissue signatures. Emphasis is on spectral/hyperspectral imaging approaches allowing the equivalent of in vivo pathology.

RESULTS

With experimental focus on unstained specimens, we demonstrate the ability to segment tissue images for cancer detection. Spectral reflectance imaging, coupled with advanced analysis, typically yields 90% specificity and sensitivity. Autofluorescence is also shown to be diagnostically useful, with lymph nodes results highlighted here. Elastic scattering hyperspectral imaging endoscopy, using a new instrument we designed and built, shows promise in bronchoscopic detection of dysplasia and early cancer in patients.

CONCLUSIONS

The results demonstrate that advanced optical imaging can detect and localize cellular signatures of cancer in real-time, in vivo, without the use of contrast agents, in animals and humans. This is an important step towards tight spatio-temporal coupling between such detection and clinical intervention.

Coherent anti-stokes Raman scattering microscopy: A biological review

Microscopic imaging of cells and tissues are generated by the interaction of light with either the sample itself or contrast agents that label the sample. Most contrast agents, however, alter the cell in order to introduce molecular labels, complicating live cell imaging. The interaction of light from multiple laser sources has given rise to microscopy, based on Raman scattering or vibrational resonance, which demonstrates selectivity to specific chemical bonds while imaging unmodified live cells. Here, we discuss the nonlinear optical technique of coherent anti-Stokes Raman scattering (CARS) microscopy, its instrumentation, and its status in live cell imaging.

Chemical images: Technical approaches and issues

Chemical mapping techniques using Raman microscopy are introduced, and using an example of a pharmaceutical tablet, the practical aspects of data collection and processing to produce a chemical image of the sample are detailed. Issues related to data processing, instrument standards, chemical image reportable errors, and the interpretation of chemical images are presented to encourage debate, develop solutions, and promote use in other challenging scientific applications. applications.